Preparation method of composite high-entropy hard carbon negative electrode material and sodium ion battery

Abstract

The application discloses a preparation method of a composite high-entropy hard carbon negative material and a sodium ion battery, and relates to the technical field of electrochemical energy storage materials.The application breaks through the existing doping limit through high-entropy design, realizes five or more than five atomic-level mixing, and has strong structural stability which cannot be realized by previous traditional binary / trinary doping.The application uses pre-assembly technology combined with step carbonization to complete "molecular anchoring" and "entropy locking", solves the pain point problem of multi-element segregation, improves the sodium storage kinetics and thermodynamic performance of the high-entropy hard carbon precursor and intermediate through careful combination design of multiple elements and subsequent carbonization process parameter optimization, realizes triple regulation of "defects-interlayer spacing-pore structure", and reduces the defect degree of the high-entropy hard carbon through the design of a coating process.The prepared composite high-entropy hard carbon negative material has excellent comprehensive performance in the sodium ion battery, and has obvious advantages in high initial coulomb efficiency, high rate capability and long stability.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials technology, and in particular to a method for preparing a composite high-entropy hard carbon anode material and a sodium-ion battery. Background Technology

[0002] In recent years, the limited, unevenly distributed, and expensive lithium resources have been unable to meet the ever-increasing energy consumption of people's production and daily life. Sodium-ion batteries, due to their abundant sodium resources, low cost, and relatively high safety, have shown great potential in the field of large-scale energy storage. However, developing high-performance, long-life, and low-cost anode materials is a key challenge for the commercialization of sodium-ion batteries. Due to the small interlayer spacing of graphite, sodium ions are difficult to embed into graphite layers, resulting in poor electrochemical performance. Hard carbon materials, due to their abundant sodium storage sites, low operating potential, and tunable structure, are considered the most promising anode materials for sodium-ion batteries. However, traditional hard carbon materials still suffer from low initial coulombic efficiency (ICE), insufficient rate performance, and inadequate long-cycle stability, which restricts the large-scale application of sodium-ion batteries.

[0003] The concept of "high entropy" has wide applications in materials science, demonstrating excellent performance control capabilities. High-entropy materials are typically composed of five or more principal elements in near-equal atomic ratios, exhibiting characteristics such as high configurational entropy, lattice distortion, slow diffusion, and a "cocktail" effect, which can significantly improve the mechanical, thermal, chemical, and electrochemical properties of hard carbon materials. Doping with metallic elements (such as Co, Mg, Ni, Sn, etc.) not only improves the conductivity of hard carbon materials but also catalyzes and regulates the growth of graphite-like microcrystals, thereby achieving the reintegration of carbon layer structures and optimization of pore structures. The introduction of non-metallic elements (such as N, P, S, etc.) can expand the carbon interlayer spacing to enhance the diffusion kinetics of sodium ions, adjust the pore structure and defect ratio to create more sodium adsorption sites, and ultimately improve electrochemical performance. However, how to utilize effective strategies to introduce non-metallic and metallic elements to prepare high-ratio, high-capacity high-entropy hard carbon materials with optimized graphite-like microcrystals and amorphous component ratios, reasonable defect sites, and abundant closed-pore structures remains a pressing challenge. Summary of the Invention

[0004] One of the objectives of this invention is to provide a method for preparing composite high-entropy hard carbon anode materials, so as to solve the problems of low initial coulombic efficiency, poor rate performance, and poor cycle stability of hard carbon anode materials;

[0005] The second objective of this invention is to provide a sodium-ion battery, including a composite high-entropy hard carbon anode material prepared therefrom.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, a method for preparing a composite high-entropy hard carbon anode material includes the following steps:

[0008] S1: Mix the mixed element doping source with the carbon source and obtain a high-entropy precursor through pretreatment;

[0009] S2: Under an inert atmosphere, the high-entropy precursor undergoes a first carbonization treatment to obtain a high-entropy hard carbon intermediate.

[0010] S3: Under an inert atmosphere, the high-entropy hard carbon intermediate undergoes a second carbonization treatment to obtain the high-entropy hard carbon material.

[0011] S4: Acid washing and deashing treatment of high-entropy hard carbon material, followed by vacuum drying, yields deashed high-entropy hard carbon material;

[0012] S5: A coating agent is added to the deashed high-entropy hard carbon material. After coating treatment, a third carbonization treatment is carried out under an inert atmosphere to obtain a composite high-entropy hard carbon anode material.

[0013] Furthermore, in S1, the carbon source is any one of bamboo powder, coconut shell, sugarcane, poplar wood, cotton, wheat, corn stalks, reeds, distiller's grains, seaweed, oak, palm shell, walnut shell, starch, and resin.

[0014] Furthermore, bamboo powder, coconut shell, sugarcane, poplar wood, cotton, wheat, corn stalks, reeds, distiller's grains, seaweed, oak, palm shell, walnut shell, or starch are crushed by a crusher and then passed through a 150-300 mesh sieve with a particle size of 50-100μm. After that, they are transferred to an oven at 70-150℃ and dried for 5-12 hours.

[0015] Furthermore, the mass ratio of the mixed element doping source to the carbon source is (0.1-10):100; the mixed element doping source consists of 5 or more types of doping sources.

[0016] Doping sources include B source, N source, O source, P source, S source, F source, Na source, K source, Mg source, Ti source, Ca source, Al source, V source, Cr source, Mn source, Fe source, Co source, Ni source, Cu source, Zn source, Mo source, Sn source, and Sb source;

[0017] The mass ratio of each dopant source to the carbon source is 0.01-0.5:10.

[0018] Furthermore,

[0019] Source B includes boric acid, borax, and boron chloride;

[0020] Nitrogen sources include urea, melamine, ammonium chloride, dopamine, and aniline;

[0021] O sources include citric acid;

[0022] P sources include black phosphorus, phosphoric acid, phytic acid, and sodium hydrogen phosphate;

[0023] S sources include thiourea, sulfur powder, and dimethyl sulfoxide;

[0024] F sources include polyvinylidene fluoride, sodium fluoride, and ammonium fluoride;

[0025] Sodium sources include sodium nitrate, sodium carbonate, sodium oxalate, sodium bicarbonate, and sodium sulfate.

[0026] K sources include potassium chloride, potassium nitrate, potassium sulfate, and potassium carbonate;

[0027] Mg sources include magnesium gluconate, magnesium citrate, magnesium lactate, and magnesium nitrate;

[0028] Ti sources include titanium monoxide, titanium dioxide, and titanium trioxide;

[0029] Ca sources include calcium gluconate, calcium chloride, calcium sulfate, and calcium carbonate;

[0030] Al sources include aluminum chloride, aluminum oxide, and aluminum nitrate;

[0031] V sources include vanadium trichloride, vanadium pentoxide, and vanadium trioxide;

[0032] Cr sources include chromium chloride, chromium nitrate, and chromium sulfate;

[0033] Mn sources include manganese nitrate, manganese chloride, and manganese acetate;

[0034] Fe sources include ferric nitrate, ferric chloride, ferric gluconate, ferric citrate, and ferrous citrate.

[0035] Co sources include cobalt chloride, cobalt nitrate, cobalt sulfate, and cobalt acetate;

[0036] Ni sources include nickel nitrate, nickel sulfate, and nickel chloride;

[0037] Cu sources include copper nitrate, copper sulfate, copper chloride, and copper acetate;

[0038] Zn sources include zinc nitrate, zinc acetate, zinc carbonate, zinc sulfate, and zinc gluconate;

[0039] Mo sources include ammonium molybdate and sodium molybdate;

[0040] Sn sources include potassium stannate, stannous chloride, and stannous tetrachloride;

[0041] Sb sources include antimony chloride and antimony acetate.

[0042] Furthermore, the pretreatment method is a mechanical mixing method. After selecting the carbon source and dopant source and adding them in a certain proportion, they are thoroughly and uniformly mixed using a mechanical mixing method, including the following steps:

[0043] The carbon source and the mixed element dopant source were physically mixed by high-energy ball milling and three-dimensional mixing ball milling for 2-10 hours, with a ball milling speed of 500-3000 rpm.

[0044] Furthermore, in S2, the inert atmosphere is Ar or N2, which can effectively prevent oxidation during the carbonization process of high-entropy hard carbon precursor powder. It has low defects and low CO content, and the prepared hard carbon material exhibits high reversible specific capacity and first coulombic efficiency.

[0045] Furthermore, in S2, the first carbonization treatment is: heating to 200-700℃ at a heating rate of 0.5-20℃ / min and holding at that temperature for 2-6 hours;

[0046] Short carbonization time, low carbonization temperature, or rapid heating rate can lead to uneven cross-linking. Hard carbon intermediates have an unstable high-entropy state structure. Long carbonization time, high carbonization temperature, or slow heating rate can cause segregation of dopants, excessive loss of dopant sources, and low yield.

[0047] By controlling the appropriate carbonization reaction time, lower carbonization temperature, and heating rate during the first carbonization process, a stable "organic-inorganic hybrid network" can be formed in the high-entropy hard carbon intermediate, locking the position occupied by the dopant element and realizing the cross-linking and solidification of the dopant source and the carbon body.

[0048] Furthermore, in S3, the inert atmosphere is either Ar or N2.

[0049] Furthermore, in S3, the second carbonization process involves heating to 1000-1800℃ at a heating rate of 0.5-20℃ / min and holding at that temperature for 2-12 hours.

[0050] Furthermore, in S3, at least one doping source can be added to the high-entropy hard carbon intermediate during the second carbonization process to assist doping, with the mass ratio of each doping source to the carbon source being (0.01-0.5):10; the mixture is then mixed by ball milling at a speed of 10-50 r / min for 1-5 h.

[0051] The second carbonization process is a high-temperature carbonization process, which further stabilizes the carbon skeleton with a high entropy effect, ensuring that the hard carbon material prepared in the end maintains a high entropy state.

[0052] By directly or in combination with other high-entropy hard carbon intermediates and calcining them at high temperatures, the carbon layers gradually twist and fold to form a rich closed-pore structure. This closed-pore structure provides ample storage sites for sodium ions, improving the reversible specific capacity of the high-entropy hard carbon material. Simultaneously, the presence of metal ions can regulate the growth of graphite domains and graphite layers in hard carbon-like graphite microcrystals and provide abundant active sites for sodium storage, which is beneficial to the migration kinetics of sodium ions. The triple coupling effect of "defect-interlayer spacing-pore structure" in high-entropy hard carbon constructs a hard carbon material that combines long sloping regions and long low plateau regions, simultaneously optimizing sodium storage kinetics and thermodynamics.

[0053] Too low a temperature, too fast a heating rate, or too short a holding time can lead to incomplete local graphite-like microcrystal growth catalyzed by metal ions, resulting in low closed pores and high defect content, exhibiting low initial coulombic efficiency and plateau capacity. Too high a temperature, too slow a heating rate, or too long a holding time will reduce the proportion of amorphous components, resulting in high-entropy hard carbon materials with low ramp capacity and poor rate performance, and the preparation process is energy-intensive and time-consuming.

[0054] Furthermore, in S4, the acid pickling and deashing treatment includes the following steps:

[0055] Add the high-entropy hard carbon material to an acid solution with a mass fraction of 5-30%, heat it to 30-100℃ on a magnetic stirrer and stir and soak it for 5-24 hours at 250-500 r / min. Filter and wash the filtrate with deionized water until it is neutral and the conductivity is less than 30 μS / cm. Dry it in a vacuum oven at 80-150℃ for 10-24 hours.

[0056] The acid solution is any one or a combination of hydrochloric acid solution, hydrofluoric acid solution, and oxalic acid solution.

[0057] The concentration of acid used in the deashing process must be reasonable. Excessive acid concentration, excessively long acid leaching time, and excessively high acid leaching temperature will damage the carbon skeleton of high-entropy hard carbon, generate more harmful defects, and reduce the initial coulombic efficiency and specific capacity of hard carbon. If the acid concentration is too low, the acid leaching time is too short, or the acid leaching temperature is too low, the ash and surface metal clusters of hard carbon cannot be removed well, and the prepared hard carbon will undergo more side reactions and severe polarization.

[0058] Furthermore, in S5, the coating agent includes phenolic resin, asphalt, tar, acetylene, methane, benzene, and toluene, and the amount of coating agent is 1-10 wt% (m coating agent / m deashed high-entropy hard carbon material).

[0059] Furthermore, in S5, the coating treatment employs either mechanical ball milling or chemical vapor deposition, depending on the type of coating agent.

[0060] Furthermore, when the coating agent is phenolic resin, asphalt, or tar, mechanical ball milling is used, specifically ball milling at room temperature for 0.5-5 hours at a speed of 500-2000 rpm.

[0061] Furthermore, when the coating agent is methane, acetylene, benzene, or toluene, chemical vapor deposition is used, specifically, under an inert atmosphere, the temperature is increased to 600-1000℃ at a rate of 2-5℃ / min for deposition for 1-5 hours.

[0062] Furthermore, in S5, the inert atmosphere is either Ar or N2.

[0063] Furthermore, in S5, the third carbonization process involves heating to 1000-1500℃ at a heating rate of 2-10℃ / min and holding at that temperature for 2-5 hours.

[0064] In a second aspect, a sodium-ion battery includes a composite high-entropy hard carbon anode material prepared in the first aspect.

[0065] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0066] 1. This invention provides a method for preparing a composite high-entropy hard carbon anode material. The core of the preparation lies in achieving uniform mixing and reaction of multiple biomass (carbon source) precursors at the molecular / atomic level, and maintaining a high-entropy state during subsequent carbonization. By introducing multiple metal / non-metal elements (five or more) and utilizing the high-entropy effect, the microstructure, defect state, interlayer spacing, and surface chemical properties of the hard carbon material are synergistically optimized. The prepared hard carbon material exhibits excellent sodium storage performance, specifically manifested in significant improvements in rate performance, initial coulombic efficiency, and long-term cycling stability.

[0067] 2. In preparing the composite high-entropy hard carbon anode material, this invention first performs low-temperature pre-carbonization on the high-entropy precursor obtained in S1, followed by high-temperature carbonization. Low-temperature carbonization of the high-entropy precursor promotes intermolecular cross-linking, removes small-molecule volatiles, further stabilizes the structure of the high-entropy precursor, and prevents elemental segregation during subsequent high-temperature carbonization, thus controlling the composition and microcrystalline structure of the hard carbon material. Specifically, the low-temperature pre-carbonization in this invention ensures the appropriate development of local graphite-like microcrystalline structures in the high-entropy hard carbon intermediate under the catalytic action of metal atoms, with amorphous components and graphite-like microcrystalline structures occupying a suitable proportion. Subsequent high-temperature carbonization is crucial for the formation of the high-entropy hard carbon structure, where diffusion and segregation of doped elements are significantly suppressed, and multiple elements achieve a uniform and stable distribution within the carbon framework. By combining the high-entropy hard carbon material with coating agents such as resin, the defect level and microstructure of the hard carbon material are improved, optimizing rate performance and initial coulombic efficiency. This invention uses "high-entropy precursor" and "high-entropy hard carbon intermediate" as the control objects, and "synergistic coupling of low-temperature pre-carbonization and high-temperature secondary carbonization" as the control method. The purpose is to control the microcrystalline structure of "high-entropy precursor" and hard carbon material prepared from "high-entropy hard carbon intermediate". Compared with traditional technology, it is simpler and more flexible, does not require additional large-scale equipment, and is suitable for large-scale industrial production.

[0068] 3. Using the prepared composite high-entropy hard carbon as an anode material in the fabrication of sodium-ion batteries can significantly improve the reversible specific capacity, initial coulombic efficiency, and rate performance of sodium-ion batteries.

[0069] 4. In summary, this invention breaks through the existing doping limits through "high-entropy design," achieving atomic-level mixing of five or more elements. It also possesses strong structural stability unattainable by traditional binary / ternary doping methods. Utilizing mechanical mixing pre-assembly technology combined with step-by-step carbonization, it achieves "molecular anchoring" and "entropy locking," overcoming the critical problem of multi-element segregation. Through careful multi-element combination design and subsequent carbonization process parameter optimization, it simultaneously improves the sodium storage kinetics and thermodynamics of the high-entropy hard carbon precursor and intermediates, achieving triple regulation of "defects-interlayer spacing-pore structure." The coating process design reduces the defect degree of high-entropy hard carbon, improving rate performance and cycle stability. Furthermore, the process designed in this invention is based on existing hard carbon production lines, requiring no new or expensive equipment, and exhibits good process compatibility. This composite high-entropy hard carbon anode material demonstrates excellent comprehensive performance in sodium-ion batteries, particularly showing significant advantages in high initial coulombic efficiency, high rate capability, and long-term stability. Attached Figure Description

[0070] Figure 1 This is a flowchart illustrating the preparation process of the composite high-entropy hard carbon anode material according to an embodiment of the present invention.

[0071] Figure 2The first charge-discharge curves of sodium-ion batteries assembled with hard carbon anode materials prepared in Example 1 and Comparative Example 5 at a current density of 30 mA / g.

[0072] Figure 3 Rate performance of sodium-ion batteries assembled with hard carbon anode materials prepared in Example 1 and Comparative Example 5 at current densities of 30-1500 mA / g.

[0073] Figure 4 The cycling performance of sodium-ion batteries assembled with the hard carbon anode materials prepared in Example 1 and Comparative Example 5 at a current density of 300 mA / g.

[0074] Figure 5 The long-cycle performance of sodium-ion batteries assembled with the hard carbon anode materials prepared in Example 1 and Comparative Example 5 at a current density of 1500 mA / g is shown in the figure. Detailed Implementation

[0075] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0076] The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. The solutions disclosed herein will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following embodiments are only for illustrating the present disclosure and should not be considered as limiting the scope of the present disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0077] The technical solution of the present invention will be further analyzed and explained through specific embodiments below.

[0078] Example 1

[0079] Please see Figure 1 The schematic diagram shown illustrates a method for preparing a composite high-entropy hard carbon anode material, comprising the following steps:

[0080] S1: Mix the mixed element dopant source (0.1g urea, 0.1g sulfur powder, 0.1g cobalt nitrate, 0.1g ammonium molybdate, 0.1g manganese acetate) and carbon source (10g bamboo powder) in a high-energy ball mill for 5 hours at a ball milling speed of 1000 rpm to obtain high-entropy precursor powder;

[0081] S2: Under an Ar atmosphere, the high-entropy precursor was subjected to a first carbonization treatment at 300℃ for 3 hours by heating at a rate of 2℃ / min to obtain a high-entropy hard carbon intermediate.

[0082] S3: Under an Ar atmosphere, the high-entropy hard carbon intermediate was subjected to a second carbonization treatment at a rate of 5℃ / min to 1300℃ for 3 hours to obtain the high-entropy hard carbon material.

[0083] S4: Immerse the high-entropy hard carbon material in a 10% (v / v) acid solution. 盐酸 :V 氢氟酸 The mixture was heated to 50°C on a magnetic stirrer and stirred at 300 r / min for 12 h. It was then filtered and washed with deionized water until the filtrate was neutral and the conductivity was less than 20 μS / cm. Finally, it was dried in a vacuum oven at 110°C for 12 h to obtain the deashed high-entropy hard carbon material.

[0084] S5: Add deashed high-entropy hard carbon material and 3wt% coating agent (phenolic resin) to the ball mill jar, and ball mill at 1000 rpm for 2 hours at room temperature to obtain high-entropy hard carbon material with phenolic resin coating structure.

[0085] Then, under an Ar atmosphere, the temperature was increased to 1300℃ at a rate of 5℃ / min for a third carbonization treatment for 3 hours to obtain a composite high-entropy hard carbon anode material.

[0086] The hard carbon anode materials of Examples 2-17 and Comparative Examples 1-5 are the same as those of Example 1, except for the experimental parameters listed in the table.

[0087] Table 1 shows some of the experimental parameters in the preparation methods of hard carbon anode materials in Examples 1-17 and Comparative Examples 1-5.

[0088] Table 1

[0089]

[0090]

[0091] Where: " / " indicates none;

[0092] Comparative Example 1 is S4 without the coating process.

[0093] Comparative Example 2 is S2 without the first carbonization treatment.

[0094] Comparative Example 3 is S1 without the addition of a mixed metal dopant source.

[0095] Comparative Example 4 is S1 without the addition of mixed metal dopant sources and S4 without the coating process.

[0096] Comparative Example 5 involves direct S3 carbonization of the carbon source, omitting the S1, S2, and S5 processes.

[0097] The hard carbon anode materials prepared in Examples 1-2 and Comparative Examples 1-5 were assembled into sodium-ion batteries, specifically including the following steps:

[0098] Hard carbon anode material, acetylene black, styrene-butadiene rubber, and carboxymethyl cellulose were mixed evenly in a mass ratio of 92:3:3.5:1.5. An appropriate amount of deionized water was added, and the mixture was ball-milled to form a uniformly dispersed paste. This paste was then coated onto copper foil to a thickness of 100 μm and dried in a vacuum oven at 80 °C for 12 h. The resulting material was then cut into 14 mm diameter circular anode sheets. CR2032 button half-cells were assembled in a vacuum glove box (water and oxygen content both below 0.01 ppm), using a sodium metal sheet as the counter electrode and a glass fiber diaphragm. The assembly was performed using 1 mol / L NaPF6 (solvent V... 碳酸乙烯酯 :V 碳酸二乙酯 A 1:1 solution was used as the electrolyte.

[0099] Reversible specific capacity test: Before electrochemical testing, the battery needs to be left to stand for more than 12 hours. Constant current charge / discharge test is performed using the Xinwei Battery Testing System. The potential range is 0-3.0V. The discharge process is as follows: the current is 30mA / g (1C=300mA / g), constant current discharge to 0V at 0.1C, left to stand for 10 minutes, and constant current discharge to 0V at 0.02C. The charging process is as follows: the current is 30mA / g, constant current charging to 3V at 0.1C.

[0100] Figure 2 This is a comparison of the first charge-discharge curves of sodium-ion batteries assembled from the hard carbon anode materials prepared in Example 1 and Comparative Example 5 at a current density of 30 mA / g. Figure 2 As can be seen, the sodium-ion battery assembled from the hard carbon anode material prepared in Example 1 has a reversible capacity of up to 483 mAh / g, an initial coulombic efficiency of 92.4%, and a slope region specific capacity of 252 mAh / g, thus exhibiting ultra-high rate performance and demonstrating great potential in the field of sodium-ion batteries.

[0101] Table 2 summarizes the test results of the first-week reversible specific capacity and first-week coulombic efficiency of the sodium-ion batteries prepared in Examples 1-17 and Comparative Examples 1-5, respectively.

[0102] Table 2

[0103]

[0104] As can be seen from Table 2, compared with Comparative Examples 3-5, the hard carbon materials obtained in Examples 1-2 all have high reversible capacity and first-week coulombic efficiency. The initial reversible specific capacity of the prepared composite high-entropy hard carbon material increased from 280 mAh / g to 483 mAh / g, and the first-week coulombic efficiency increased from 85.8% to 92.4%. It can be seen that by designing a high-entropy coupling multi-stage carbonization and coating process for biomass carbon source, the reversible specific capacity and first-week coulombic efficiency of biomass hard carbon anode material were significantly improved.

[0105] Figure 3 The graphs show the rate performance of sodium-ion batteries assembled with the hard carbon anode materials prepared in Example 1 and Comparative Example 5 at current densities of 30-3000 mA / g. It can be seen that the carefully designed composite high-entropy hard carbon material has enhanced rate performance, increasing from 93 mAh / g in Comparative Example 5 to 174 mAh / g in Example 1 at a current density of 3 A / g, demonstrating rapid sodium-ion migration kinetics.

[0106] Figure 4 The graphs show the cycling performance of sodium-ion batteries assembled with the hard carbon anode materials prepared in Example 1 and Comparative Example 5 at a current density of 300 mA / g. It can be seen that the composite high-entropy hard carbon material has high cycling stability.

[0107] Figure 5 The graph shows the long-cycle performance of sodium-ion batteries assembled with the hard carbon anode materials prepared in Example 1 and Comparative Example 5 at a current density of 1500 mA / g. It can be seen that the composite high-entropy hard carbon material has long-cycle stability and reversible specific capacity at high current density.

[0108] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0109] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite high-entropy hard carbon anode material, characterized in that, Includes the following steps: S1: Mix 0.1g of mixed element doping source (urea), 0.1g of sulfur powder, 0.1g of cobalt nitrate, 0.1g of ammonium molybdate, 0.1g of manganese acetate) with 10g of carbon source (bamboo powder) in a high-energy ball mill for 5 hours at a ball milling speed of 1000 rpm to obtain high-entropy precursor powder. S2: Under an Ar atmosphere, the high-entropy precursor was subjected to a first carbonization treatment at 300℃ for 3 hours by heating at a rate of 2℃ / min to obtain a high-entropy hard carbon intermediate. S3: Under an Ar atmosphere, the high-entropy hard carbon intermediate was subjected to a second carbonization treatment at a rate of 5℃ / min to 1300℃ for 3 hours to obtain the high-entropy hard carbon material. S4: Immerse the high-entropy hard carbon material in a solution with a mass fraction of 10% V. 盐酸 :V 氢氟酸 In a 1:1 acid solution, the mixture was heated to 50°C on a magnetic stirrer and stirred at 300 r / min for 12 h. It was then filtered and washed with deionized water until the filtrate was neutral and had a conductivity of less than 20 μS / cm. Finally, it was dried in a vacuum oven at 110°C for 12 h to obtain a deashed high-entropy hard carbon material. S5: Add deashed high-entropy hard carbon material and 3wt% coating agent phenolic resin to the ball mill jar, and ball mill at 1000 rpm for 2 hours at room temperature to obtain high-entropy hard carbon material with phenolic resin coating structure. Then, under an Ar atmosphere, the temperature was increased to 1300℃ at a rate of 5℃ / min for a third carbonization treatment for 3 hours to obtain a composite high-entropy hard carbon anode material.

2. The method for preparing a composite high-entropy hard carbon anode material according to claim 1, characterized in that, Includes the following steps S1: Mix 0.1g of mixed element doping source (urea), 0.1g of sulfur powder, 0.1g of cobalt nitrate, 0.1g of ammonium molybdate, 0.1g of manganese acetate) with 10g of carbon source (bamboo powder) in a high-energy ball mill for 5 hours at a ball milling speed of 1000 rpm to obtain high-entropy precursor powder. S2: Under an Ar atmosphere, the high-entropy precursor was subjected to a first carbonization treatment at 300℃ for 3 hours by heating at a rate of 2℃ / min to obtain a high-entropy hard carbon intermediate. S3: Add 0.1g aluminum chloride, 0.1g chromium sulfate, and 0.1g antimony chloride as auxiliary dopant sources to the high-entropy hard carbon intermediate. Under an Ar atmosphere, heat the intermediate to 1300℃ at a rate of 5℃ / min for a second carbonization treatment for 3 hours to obtain the high-entropy hard carbon material. S4: Immerse the high-entropy hard carbon material in a solution with a mass fraction of 10% V. 盐酸 :V 氢氟酸 In a 1:1 acid solution, the mixture was heated to 50°C on a magnetic stirrer and stirred at 300 r / min for 12 h. It was then filtered and washed with deionized water until the filtrate was neutral and had a conductivity of less than 20 μS / cm. Finally, it was dried in a vacuum oven at 110°C for 12 h to obtain a deashed high-entropy hard carbon material. S5: Add deashed high-entropy hard carbon material and 3wt% coating agent phenolic resin to the ball mill jar, and ball mill at 1000 rpm for 2 hours at room temperature to obtain high-entropy hard carbon material with phenolic resin coating structure. Then, under an Ar atmosphere, the temperature was increased to 1300℃ at a rate of 5℃ / min for a third carbonization treatment for 3 hours to obtain a composite high-entropy hard carbon anode material.

3. A sodium-ion battery, characterized in that, The composite high-entropy hard carbon anode material prepared by the preparation method according to any one of claims 1-2.

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